1. Field of the Invention
The present invention relates to a paper feeder for interposing, between two rollers, a sheet of paper supplied from an upstream section, and feeding the sheet of paper to a downstream section in accordance with rotation of the rollers. The present invention also relates to a printer provided with the paper feeder.
2. Description of the Related Art
A paper feeder, which may be carried on an ink-jet printer, has been hitherto known, for interposing, between two rollers, a sheet of paper supplied from an upstream section, and feeding the sheet of paper to a downstream section in accordance with rotation of the rollers.
Such a paper feeder has, for example, a structure as shown in FIG. 5. Namely, the paper feeder comprises, for example, a feed roller 51 to be driven and rotated by power transmitted from a motor or the like, a support shaft 53 spanned in parallel to the feed roller 51, an arm 55 swingably attached to the support shaft 53, a pressure roller 57 rotatably supported by a shaft disposed at a tip of the arm 55, and springs 59 arranged in a compressed state between the arm 55 and fixtures mounted on a main body (not shown). The arm 55 is energized by the springs 59 so that the pressure roller 57 is pressed against the feed roller 51. A sheet of paper is fed to a downstream section by using frictional force between the feed roller 51 and the sheet of paper in accordance with rotation of the feed roller 51 while interposing the sheet of paper between the feed roller 51 and the pressure roller 57.
In general, one feed roller 51 involves a plurality of the aforementioned pressure rollers 57 which are arranged along an axial direction. Such an arrangement is significant when a sheet of paper having irregularities is fed, or when the feed roller 51 has irregularities due to damage or wearing, because each of the pressure rollers 57 corresponding to each part of the sheet of paper in its widthwise direction individually moves and presses the sheet of paper in response to the irregularities on the feed roller 51 and the sheet of paper. Accordingly, sufficient frictional force is generated between the feed roller 51 and the sheet of paper. Thus, the sheet of paper is smoothly fed by the aid of the feed roller 51.
However, the pressure roller 57 is a component part made of metal produced in accordance with a precise cutting process, and the pressure roller 57 is relatively expensive as compared with other component parts made of resin. Therefore, a problem has hitherto arisen in that arrangement of an excessively large number of the pressure rollers 57 is disadvantageous in view of the cost.
Now, only from a simple viewpoint of cost reduction, the number of the pressure rollers 57 can be decreased by allowing the pressure roller 57 to have a length L longer than those hitherto used. However, if the length L of the pressure roller 57 is too long exceeding a certain extent, it is feared to exert, for example, the following bad influences. Namely, when the irregularities as described above are present, the load given by the pressure roller 57 is concentrated on portions corresponding to protrusions, while the load given by the pressure roller 57 scarcely applied to portions corresponding to depressions. As a result, the sheet of paper is not contacted with the feed roller 51 with sufficient pressure at the portions corresponding to the depressions, giving rise to partial shortage in frictional force between the feed roller 51 and the sheet of paper to cause, for example, inclination of the feeding direction for the sheet of paper.